This disclosure generally relates to elevator systems. More particularly, this disclosure relates to an elevator braking system.
Elevator systems include a braking system to hold an elevator car in a desired position, such as at a landing. Typically, the elevator system includes an elevator machine that moves the elevator car between landings. Once at a desired landing, the braking system applies a braking force to hold the elevator car at the landing.
The braking system typically includes springs that bias a moveable plate against a brake rotor that rotates with a machine shaft extending from the elevator machine. The brake rotor includes a brake lining. The resulting friction between the brake lining and the moveable plate holds the elevator car, or in some circumstances is used to slow the movement of the elevator car. Engagement between the moveable plate and the brake lining is the default condition. The moveable plate is disengaged from the brake lining by applying a magnetic field using an electromagnet. An attractive force generated by the magnetic field overcomes the bias force of the springs and lifts the moveable plate away from the brake rotor and brake lining to permit the elevator car to move.
Although effective, conventional arrangements that depend on friction may have the drawback that the brake lining is vulnerable to wear. Over time, the brake lining may wear down and cause variation in the amount of braking force applied by the springs. Additionally, the wear may increase the distance between the moveable plate and the electromagnet and require a stronger magnetic field to lift the moveable plate off of the brake lining.
Accordingly, there is a need for a braking system that provides a desired braking force without friction.